The invention relates to a double-walled structure, such as double-walled segment, preferably for use in ventilation ductwork systems. The invention also relates to a connection arrangement for coupling together two double-walled segments, preferably for use in a ventilation ductwork system.
Double-walled structures for use in ventilation duct systems are well known in the art. Such double-walled structures may be comprised of a one piece straight elongated duct, an elbow, a connecting element, a silencer, etc. xe2x80x9cDouble-walled structurexe2x80x9d refers to a structure having an inner tube forming an inner wall of the structure, and an outer casing, being spaced from the inner wall and forming the outer wall of the structure. The space between the inner and outer walls is filled by insulating material, e.g. a sound insulating or absorbing material. In U.S. Pat. No. 5, 801,342, the specification of which is hereby incorporated by reference, a sound absorbing double-walled structure is disclosed, having its inner tube or inner wall formed in the shape of a helically-wound lock-seam tubing and an outer casing, and having its outer casing or outer wall typically also formed of a helically-wound lock-seam tubing. The inner tube is perforated, and the sound absorbing material in the space between the inner tube and the outer casing is preferably wool.
It is understood that installation of duct systems, including double-walled duct systems for ventilation purposes, in buildings, mostly requires coupling together of two similar or different segments, such as straight elongated segments, elbows, etc. For this purpose one of the two segments to be coupled together is provided, at one end, with a female portion and the other of the two segments to be coupled together is provided, at one end, with a male portion, which one ends of the two segments are designed such that the male and female end portions can be interconnected with a fit, such as a slip fit. The male portion may have a gasket, such as a lip seal, on its outer circumference for sealing against the inner circumference of the female portion, when the segments are coupled together.
Coupling together of two double-walled segments with a male portion and a female portion, respectively, at one end is more complicated than coupling together of two single-walled segments. This is because interconnecting of the male and female end portions of two double-walled segments requires, in fact, connecting of four tubings, which connecting, to be time-effective, should be done simultaneously, in a single push-together movement. To achieve this, there must be a perfect alignment between the male and female end portions of the segments to be interconnected. However, no such perfect alignment can be achieved quickly in practical application, especially not when the coupling of the segments is to be done in overhead areas, e.g. near the ceiling of a building, requiring raised arms of the installer, or in confined spaces. The difficulty involved is illustrated in FIG. 1, relating to prior art technique for coupling together two double-walled segments 1 and 2. When these two segments are to be coupled together at their male and female end portions and there is no alignment between them, the protruding inner tube 2A, defining a male portion, of segment 2 binds on or snags the inner tube 1A , defining a female portion, of segment 1. Attempts to adjust the inner tubes 1A and 2A for alignment, thereby making them capable of a slip fit, does not assure that the outer tubes or casings 1B and 2B will also have an orientation which is correct for a slid fit between the outer casings 1B and 2B. Such a situation requires repeated efforts to be made by the installer in order to make both the inner tubes 1A and 2A and the outer casings 1B and 2B register in alignment, such that a correct overlapping slip fit connection between all four tubes 1A, 1B and 2A and 2B, respectively, can be made. As understood, such efforts are more accentuated, when dealing with inner tubes/outer casings having a non-circular cross section, e.g. oval or rectangular (square), which is preferred by some customers.
There is another aspect, specially related to coupling of two double-walled segments, having an insulating material filling the space between the inner wall and the outer wall, for use in a ventilation system. This aspect is the prevention of the insulating material, mostly fibrous material, e.g. glass fiber, from being drawn into the air duct, i. e. the inner tube thereof, which would impair the sound-absorbing effect of the air ductwork and also would entail the risk of breathing in fibrous material. In U.S. Pat. No. 5,081,342 a fluid-impermeable cover is applied on the outside of the perforated inner tube for said prevention. However, no mention is made there of how to prevent insulating material from being drawn into the air duct in a joint or connection between two double-walled segments.
An object of the invention is to eliminate the drawbacks mentioned above by providing an improved double-walled structure, making it possible to connect two double-walled segments together in a simple way. This object is achieved by a double-walled structure according to the attached claims.
Thus, the structure according to the invention requires only that the outer casings of two double-walled segments to be coupled together have a male part and a female part, respectively, to be interconnected, making the coupling easier than the prior art technique, requiring coupling of four tubes. The seal(s) provide support when carrying out the connection of the male/female ends of the two outer casings and isolate the insulation from the air stream in a ventilation ductwork system. The seals further may have the function of the batting/filling in the space between the inner tubes and outer casings of the segments, e.g. a sound absorbing function, and/or a thermal insulation function in the joint between the coupled segments.